Method of producing rolled steel having high-strength and low-impact transition temperature

ABSTRACT

Rolled steels characterized in their as-rolled condition by an unexpected combination of high-strength and low-impact transition temperature. The product is produced by rolling a steel workpiece containing both austenite and ferrite, preventing complete recrystallization at any time thereafter, and continuing the rolling of said workpiece as it is cooling in the temperature range between the Ar1 temperature and 600* F.

15] 3,545,801 [451 Feb. 29, 1972 METHOD OF PRODUCING ROLLED STEEL HAVINGHIGH STRENGTH AND LOW IMPACT TRANSITION TEMPERATURE George F. Melloy;Joseph D. Dennison, both of Bethlehem, Pa.

Bethlehem Steel Corporation Filed: Dec. 20, 1968 Appl. No.: 786,844

Related US. Application Data Continuation-impart of Ser. No. 741,372,June 27, 1968, abandoned.

inventors:

Assignee:

[56] References Cited UNITED STATES PATENTS 3,264,144 8/1966 Frazier etal.... ..148/12 3,423,252 1/1969 Grange 148/12 3,432,368 3/1969 Nakamura148/12 3,459,599 8/1969 Grange 148/12 Primary Examiner-L. DewayneRutledge Assistant Examiner-W. W. Stallard Attorney-Joseph .I. OKeefe[57,] ABSTRACT Rolled steels characterized in their as-rolled conditionby an unexpected combination of high-strength and low-impact transitiontemperature. The product is produced by rolling a US. ,J Steel kpi t i ig b th au te ite a d ferrite prevent- Czld tg ing completerecrystallization at any time thereafter, and cono arc tinuingtherolling of said workpiece as it is cooling in the tem.

- perature range between the Ar temperature and 600 F.

nciaims, 3 Drawing Figures 16L 1 +100 I I g LOW-FINISHING I;TEMPERATURE- ROLLING O: +50 E: g I I I e B I E HOT g w ROLLING F I I trA-E Q l g i E 2 J -loo a: e I O I I 1 N D CONIgNUUh R LLIN I E 1M -2oo Iw I 5O 6O I00 I I0 YIELD POINT OR YIELD STRENGTH FZSJ. (Thousands) MI/E/VTOR QQW George /T Me//0y Jase 0h D Denn/son QQQ PATENTEDFEBZS I972sum 1 0F 3 PATENTEDFEBZS I972 sum 2 OF 3 Q83 QQQ QSKQQQQ-ak 239% K Qwoau 3% 1d NR ERQM w M K 83%? N IIII- lI-lllllllI-l'l M R Hawk t /m m mWm m w 0 (1,) amzwadmu emu/yam WIN/J METHOD OF PRODUCING ROLLED STEELHAVING HIGH-STRENGTH AND LOW-IMPACT TRANSITION TEMPERATURECROSS-REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 741,372, filed June 27,1968 and now abandoned.

BACKGROUND OF THE INVENTION This invention is directed to rolled steeland a method of producing the same. For convenience, the method issometimes hereinafter called continuum rolling."

Normal practice used to produce hot-rolled steel consists of heating thesteel to a temperatureat which it is fully austenitic and then reducingthe steel to final dimensions as rapidly as possible with a minimum ofheat loss, generally finishing above the Ar temperature. Such practicetakes advance of ease of working at high temperature, but does notdevelop the combination of desirable properties possible of developmentin as-rolled steel.

Prior studies have shown that higher strength can be developed in thesteel by use of low-finishing-temperature rolling. In this practice, thesteel is heated and partially reduced while austenitic, as in hotrolling. Further reduction of the cross section is then delayed to allowthe workpiece to cool to a lower-than-normal temperature after whichrolling is continued to the final desired cross section in one or morepasses.

In these prior art practices, the cross-sectional area of the workpieceis reduced to final size and'shape in a sequence of rolling passes. Suchpasses may include two general types, those intended mainly to reducethe cross-sectional area of the workpiece and those intended mainly forgage or shape and which may be accompanied by relatively littlereduction. As a matter of economy, a rolling sequence should comprise afew passes as possible or practical. Each pass intended primarily forreduction should therefore effect as great a reduction incross-sectional area as possible or practical. Further, it is known thatdevelopment of the aforementioned higher strength bylow-finishing-temperature rolling requires reduction of cross-sectionalarea of approximately percent or more at the lower-than-normaltemperature.

In low-finishing-temperature rolling, it isknown that the steel isstrengthened and its impact transition temperature is decreased bylowering the finishing temperature below the Ar temperature. It is alsoknown that further strengthening is obtained by further lowering thefinishing temperature below the Ar temperature, but impact transitiontemperature is thereby increased. In contrast, we have found that by useof continuum rolling, such further strengthening is accompanied by adecrease rather than an increase in impact transition'temperature. Thiscombination ofhigh strength and low impact transition temperature is anunexpected and very desirable combination of properties.

SUMMARY OF THE INVENTION The steels of this invention are characterizedin their asrolled condition (a) by having greater strengths and lowerimpact transition temperatures than steels of the same compositionproduced by hot rolling and (b) by having lower impact transitiontemperatures than steels of the same composition produced to the samestrength by low-finishing-temperature rolling.

Broadly, the method of this invention comprises:

1. providing a steel workpiece at a temperature at which it isessentially completely austenitic,

2. rolling said workpiece as it is cooling in the temperature rangebetween the Ar; and Ar, temperatures,

3. continuing the rolling of said workpiece as it is cooling in thetemperature range between the Ar, temperature and 600 F., and 4.preventing complete recrystallization at any time after completion ofstep 2.

The benefits of the invention are primarily applicable to steelscontaining not more than 0.35 percent carbon and not more than a totalof 3 percent of other elements other than iron.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showingthe relationship between typical cooling curves of steel plates andcurves representing various percentages of recrystallization.

FIG. 2 shows a possible continuum rolling sequence superimposed on arecrystallization diagram similar to FIG. 1.

FIG. 3 is a graph comparing impact transition temperatures and yieldpoints or yield strengths of steel of a particular composition producedby continuum rolling with those of steel of the same compositionproduced by (1) hot rolling and (2) low-finishing-temperature rolling.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of this inventiondiffers from prior art methods in that (a) the steel must be rolled intwo temperature ranges, namely, between the Ar and the Ar temperaturesand between the Ar temperature and 600"v F. and preferably in threetemperature ranges, namely, the two first-mentioned temperature rangesand the hot-rolling temperature range and (b) complete recrystallizationat any time after completion of the rollingin the Ar -Ar temperaturerange must be avoided.

The workpiece for rolling in the Ar -Ar, temperature range is a steelworkpiece at a temperature at which it is essentially completelyaustenitic. Various methods of obtaining said workpiece will berecognized by those skilled in the art but preferably said workpiece isobtained by hot rolling. The amount of reduction in such hot rolling isnot critical, but from a practical viewpoint it is helpful to take asmuch reduction as possible because of ease of working. Such rolling inthe Ar -Ar temperature range must be carried out as the workpiece iscooling in that range and must comprise one or more rolling passesincluding at least one reduction pass. The meaning of theterm reductionpass, as used herein, encompasses both'a single pass in which thereduction of the cross-sectional area of the workpiece is at least 15percent and two or more passeseffecting an amount of reduction and takeninrapid enough succession to prevent any recrystallization betweenpasses.

Following the rolling in the Ar -Ar,. temperature range, rolling must becontinued as the workpiece is cooling in the Ar,-600 F. temperaturerange and must comprise one or more rollingpasses in that rangeincluding at least one reduction pass.

Conditions following the rolling in the Ar Ar, temperature range must besuch that complete recrystallization of the deformed grains produced bythe last reduction pass in said temperature range does not take place atany time after such last reduction pass and preferably such thatpercentage recrystallization does not exceed 60 percentat any time aftersuch last reduction pass.

As used herein, percentage recrystallization means the cross-sectionalarea of recrystallized grains expressed as apercentage of totalcross-sectional area on a plane transverse to the direction of maximumelongation of the workpiece during rolling.

FIG. 1 illustrates diagrammatically the principles upon which reductionin the Ar -Ar, range and in the Ar,-600 F. range depend. In the FIGURE,the abscissa represents time on a logarithmic scale with zero timerepresenting the time at completion of a reduction pass. The ordinaterepresents temperature, with the Ar;, and Ar, temperatures indicated.Lines 1, 2, and 3 represent, respectively, times and temperatures forcommencement of, 60 percent and percent recrystallization. Lines 4, 5,6, 7, and 8 represent the cooling of steel workpieces. It will beunderstood that the values shown in the FIGURE are illustrative only;actual values depend on the actual workpieces being considered and canbe determined by known methods.

As stated hereinabove, it is necessary to roll the workpiece in the Ar-Ar range and to follow such rolling by rolling in the Ar,-600 F. rangewhile maintaining conditions such that complete recrystallizationisavoided and preferably such that recrystallization does not exceed 60percent at any time after completion of the last reduction pass in thefirst-mentioned rolling. In the FIGURE, Point A on Line 8 indicates atemperature to which a steel workpiece has cooled and which is withinthe Ar -Ar, range. Line represents the cooling of said workpiece afterit has been given a reduction pass at the temperature represented byPoint A. It will be seen that as said reduced workpiece cools along Line5, it completely recrystallizes before it cools to a temperature belowthe Ar temperature, thus becoming unsuitable for the subsequentreduction in the Ar -600 F. range. There are ways of meeting thissituation. One way is to accelerate the cooling of said reducedworkpiece by water sprays, air blasts or the like so that it cools to atemperature below the Ar, temperature while avoiding completerecrystallization, as shown for example by Line 4. A second way is toallow said reduced workpiece to cool as shown by Line 5 to a temperatureas indicated for example by Point B and then to give it a secondreduction pass within the Ar -Ar range. As shown by Line 6, suchtwice-reduced workpiece cools to a temperature below the Ar, temperaturewith less than 60 percent recrystallization. A third way is to allow theaforementioned workpiece of Line 8 to cool to a lower temperature, asindicated for example by Point C, and then to give it a reduction passwithin the Ar -Ar range. The cooling of such reduced workpiece is alsoshown by Line 6.

As .stated hereinabove, complete recrystallization of the steel at anytime after the last reduction pass in the Ar -Ar, range must beprevented. In FIG. 1, Line 7 represents the cooling of a steel workpieceafter a reduction pass at a temperature below the Ar, temperature. It isseen that recrystallization is avoided as such reduced workpiece cools.However, if the temperature at which a reduction pass is effected andthe cooling and recrystallization characteristics of the resultingreduced workpiece are such that it would recrystallize before beinggiven another reduction pass or before cooling to a temperaturesufficiently low to prevent recrystallization, then the cooling of saidreduced workpiece must be accelerated by water sprays, air blasts of thelike so as to prevent complete recrystallization and preferably so as toprevent exceeding 60 percent recrystallization.

FIG. 2 illustrates diagrammatically a possible rolling sequence forproducing a /-inch plateby continuum rolling. In the FIGURE the abscissarepresents time on a logarithmic scale, with zero time representing thetime at completion of a reduction pass. The ordinate representstemperature on an arithmetic scale, with Ar, and Ar, temperaturesindicated. Lines l3 represent times and temperatures for commencementof, 60 percent, and 100 percent recrystallization. The horizontal dashedlines represent instantaneous return to zero time. In this example, a2%-inch slab has been rolled from A 4- inch slab at temperatures wellabove the Ar,, temperature and, as shown in the FIGURE, has air cooledin about 2 minutes to about,l,720 F. This 2%-inch slab is given twopasses at temperatures above the Ar temperature, first to 2% inches (A)and then 1% inches (B). After each of these passes the plate cools inair for about 2 minutes, cooling during the latter period to about 1,385E, somewhat below the Ar temperature.

In the Ar -Ar, temperature range the steel is given two passes, first to1% inches (C) and then to 1 inch (D). After a each of these passes theplate cools in air for about 2 minutes,

cooling during the latter period to about 1,160 F., somewhat below theAr, temperature. Percentage recrystallization following the first passis small, and there is no recrystallization following the second pass.

In the temperature range between the Ar temperature and 600 F. the steelis given three passes, first to 3 1 inch (E), then to is inch (F), andfinally to V2 inch (G). After each of the first two of these passes tothe plate cools in air for about 2 minutes; after the final pass, theplate cools in air to room temperature. There is no recrystallizationfollowing any of these passes.

All of the passes in this rolling sequence are reduction passes and itis to be understood that such other passes as may be necessary can beincluded provided that percentage recrystallization is controlled ashereinabove described. Also, the cooling periods of about two minutes inair were chosen as a matter of convenience and it is to be understoodthat percentage recrystallization can be controlled with differentcooling periods and different cooling methods as hereinabove described.

Following are descriptions of specific examples of plates produced bycontinuum rolling and by prior art methods.

Thirteen plates were made of steel having the following nominalpercentage composition:

c Mn P s Si Al Cb N, 0.052 L08 0.01 0.015 0.02 0.005 0.03 0.002

balance substantially iron.

4-inch thick slabs of this steel were heated to a temperature of 2,200F. and rolled to /2-inch plate in accordance with the followingschedule: I

' Box pass to obtain width.

The Ar;, and Ar, temperatures of this steel were 1,500 F. and 1,320 F.respectively at a cooling rate of approximately 1,000 F ./hr.

Table 1 shows the temperature ranges in which the above reductionschedule was carried out. Plates A-I-I are illustrative of platesproduced by prior art rolling methods, while Plates J-N are illustrativeof plates produced by continuum rolling. The recrystallizationcharacteristics of the steel and the cooling rates and intervals betweenpasses were such that in the rolling of Plates JN the percentagerecrystallization did not exceed 60 percent at any time after completionof the reduction in the Ar -Ar temperature range.

Table 2 shows the finishing temperature, yield point or yield strength,tensile strength, elongation, and V- l 5 Charpy impact transitiontemperature of each of the thirteen plates A-N.

FIG. 3 shows for the said 13 plates the manner in which impacttransition temperature varies with strength as dependent on the methodof rolling. In the FIGURE, points A, B, and C represent plates producedby hot rolling, points I) and E represent plates finished attemperatures between the Ar and the Ar, temperatures bylow-finishing-temperature rolling, points F, G, and H represents platesfinished at temperatures below the Ar, temperature bylow-finishing-temperature rolling, and points J, K, L, M, and Nrepresent plates produced by continuum rolling. Both the FIGURE andTable 2 show clearly that the plates produced by continuum rolling havehigher strengths and lower impact transition temperatures than do thoseproduced by hot rolling. Moreover, Table 2 shows clearly that finishingthev rolling at temperatures below the Ar temperature either bylow-finishing-temperature rolling or by continuum rolling increased thestrength of the steel over that obtained by finishing the rolling attemperatures above the Ar, temperature. However, the importantdistinction shown by both the TABLE and the FIGURE is that when suchfurther strengthening is by low-finishing-temperature rolling impacttransition temperature is raised as strength is increased, whereas whensuch further strengthening is by continuum rolling impact transitiontemperature is lowered as strength is increased. The difference issubstantial. For exam- 5 A though th method of this invention has beendescribed ple, the dashed lines on the FIGURE show that lo -finihingonly in connection with the rolling of plates, the method maytemperature rolling could provide a plate with a yield strength he u din t rolling of other Products Such as l bars. of 75,000 p.s.i. and animpact transition temperature of apstructural Sections and thelikeproximately plus 80 F., whereas continuum rolling could pro- Allreferences herein to Steel compositions in terms of P vide a plate ofthe same strength with an impact transition Femages are weightPercentagestem rature nearl 200! er, e1. r "5 y ow nam y app oximatelyminus TABLE 1 Table 3 gives the percentage compositions of seven other 15 gg g gg steels from which specific examples of plates were produced Nb mt inol ies' d f l by continuum rolling and by prior art methods. Ineach of Plate @52 :28: From To Re $133; these steels the balance of thecomposition was substantially Hot mmng iron. Varieties included aresemikilled, killed, carbon, low al- A loy, bainitic, and precipitationhardening steels. grifiiyg; 2 3:

The Ar; and Ar, temperatures of the Table 3 steels at 0001- 11 i -M 4 167- ing rates of approximately 1 ,000 F./hr. are shown in Table 4.Low-finishing-temperature rolling D 10 2200-1500 4 84,3 1 1, 9g 20.0Table4 .E 8 2, ZOO-1,500 4 1 76.0 3 1, 5004,4415 1 16 50.0 10 2, 200-1,800 4 84.3 1 1, 310 E 20.0 N 10 2, 200-1, 800 4 5 84.3 0. Al, r 1 1 l1520 F. I400 F. H 10 2, 200-1, 800 4 84.3 2 1520 F. 1320 F. 1 95 16 0 a1500 F. 1300 F. Cdhtmuum mmng 4 1440 F. [220 F. 7 2 20 1 500 4 1% 65 6 5J 2 11500-11320 1% 45:4 6 1400 F. 1 160 F. 2 320. 2 5 M2 33 3 7 1140" F.950 F. 6 2, 200-1, 500 4 1% 50. 2 35 ,K 2 1,500-1,a20 1% i 42.8 aam-1,000 1 -15 50.0 5 2,'200-1,500 4 255 45.8 L 2 1,500-1,320 2% 1% 35.3One or more slabs of each of the compositions specified in 2 2 1% g:Table 3 were rolled to 10-inch plate by continuum rolling. For M 2 1:500- '320 2% 1% 33.3 comparative purposes, one or more slabs of eachcomposition 40 2 2' Q: 2 were also rolled into r-inch plate by prior artrolling methods. N 2 320 w 3 5 1, 320-025 1% 71. 5 The details of therolling practices, and the resulting yield strengths or yield points,tensile strengths, and V-l5 Charpy impact transition temperatures areset forth in Tables 5-1 1. TABLE 2 In reference to the data set forth inTables 5-11, it is well V45 cm m Percent impact that and Impact f fmmperamre of 8 Finishing Yield Tensile elongation transition steel areaffected both by the composition of the steel and by the temgerapoint,strength, temperatglrFe, way in which it is proeesed. For example,Tables 5-1 1 show a Plate inch 3 inch wide range of strengths and impacttransition temperatures for Hot mmng steels of seven differentcompositions each of which was rolled 1, 840 40, 400 +5 by prior artmethods and by one or more examples of cona 221% 24 3. tlnuum rolling,wh le Table 2 shows a wide range of strengths Lowmhmgmmpemm mmng andimpact transition temperatures for a steel of a particular 0 compositionrolled in a number of ways, including several dif- 3 2 g 83 222% 1,31059,500 74, 300 31 -5 ferent examples of continuum rolling. Every plateproduced 1,130 67 100 76,100 28 +40 by continuum rolling has anunexpectedly good combination 910 '77, 500 83,600 25 90 of strength andimpact transition temperature, but for the Continuum mmng reason citedabove it is not poss ble to broadly characterize J n 1, 205 Gallon 71200 18 the product of continuum rolhng in terms of specific values of K,030 500 3, 0 2 1: 1% those properties. As said earlier, the products ofcontinuum a- 338- 32% f 400 rolling are characterized in their as-rolledcondition (a) by N 625 113,700 15 having greater strengths and lowerimpact tia nsition tempe a- 65 Yield strength (0.2% oflset).

TABLE 3 Composition (percent) Number Type C Mn P S Si Ni Cr Mo Cu A1 VCb B N Very low CMnV. .002 1.06 .009 .018 .02 .01 .01 .008 .01 .005 .06Nil Nil .002 w C-Mn .05l 0.13 .008 .015 .02 .02 .01 .002 .01 .005 .002Nil Nil .00i Low C-Mri-V-N.-. .050 1.08 .009 .015 .02 .03 .01 .008 .01.005 .07 N11 N11 .008 Low alloy .10 .09 .083 .025 .30 .71 .57 Nil .24.006 .003 Nil Nil .007 -Mn .28 1.11 .020 .032 .20 .03 .04 Nil .05 .043.002 Nil Nil .005 1% copper.. .24 1.08 .014 .015 .33 .02 .01 Nil 1.00.079 .003 Nil Nil .008 ainiti .12 1.05 .011 .014 .20 .04 .50 .50 .02.030 .003 Nil .003 .00

tures than steels of the same composition produced by hotrolling and (b)by having lower impact transition temperatures than steels of the samecompositions produced to the same strength by low-finishing-temperaturerolling.

" TABLE [Steel No. 1-Very low C-Mn-V] Yield Tensile a i? 02 1 Reductionpractice 3: 1 33;22: 3 355? l gt t s p n t 12 3 l l git temperatyrlgtHot rolling. 11 2, 200-1, 710 4' 4 2 200-1 520 4"- 2 Continuum rolling 29 TABLE 6 [Steel No. 2-Low C-Mn] V-l5 Ch y Yield Tensile transi t i nNumber Temperature Thickness, Reduction, point, strength, temperature,Reduction practice of passes range, F. inches percent K s.i. K s.i. FHot rolling 11 2, 200-1, 700 4' }5' 87. 5 32. 4 49. 4 6 2, 200-1, 6204'- 1 66. 2 Continuum rolling 2 1, 520-1, 320 1%'- 1' 42. 8 2 1, 320-1,100 1 50. 0 63 7 74. 4 -110 4 2, 200-1, 520 2 -25% 34. 4 Do 2 1,sac-1,220 2%' 1 33.3 5 -890 1%'- 71 5 '69 2 77. 2 -285 TABLE 7 [SteelNo. 3Low C-Mn-V-N] V-lfi Ch 7 Yield Tensile transi t i n NumberTemperature Thickness, Reduction, point, strength, temperature,Reduction practice of passes range, F. inches percent K s.i. K s.i. F,Hot rolling 11 2, 200-1, 610 4-%" 87. 5 49. 3 01. 9 Do 10 2, 200-1, 6054"-+%" 87. 5 65. 0 02. 1

e 2, 1, 500 4"-- 1 50. 2 Continuum rolling 2 1, 600-1, 300 1%"-- 1" 2 1,300-1, 205 1"-%" w 'Xield strength (0.2% oflset).

TABLE 8 [Steel No. 4-Low alloy] V-lfi Charpy Yield Tensile transitionNumber Temperature Thickness, Reduction, point, strength, temperature,Reduction practice of passes range, F. inches percent K s.i. K 5.1. F.Hot rolling 11 2, 1, 700 90. 0 Do 11 2, 1, 490 90. 0Low-flnishing-temperature 10 2, 200-1, 850 87. 6 rolling 1 1, 320 20. 05 2, 200-1, 450 57. 5 Continuum rolling 3 1, 440-1, 220 61. 0 1 0 39. 8

Yield strength (0.2% oflset).

TABLE 9 [Steel No. 5--CMn (ki1led)] V-15 Charpy Yield Tensile transitionNumber Temperature Thickness, Reduction, point, strength, temperature,Reduction practice oi passes range, F. inches percent K s.i. K s.i. F.Hot rollingll 2, 200-1, 740 91. 7 o 0 2,200-1,500 91.7Low-Finishing-Temperature 10 2, 200-1, 850- 89. 5 Rolling. 1 1, 310 20.0 5 2, 200-1, 400 04.0 Continuum rolling 2 1, 400-1, 200 35. 3 2 1,200-1, 63. 6 Yield strength (0.2% offset).

TABLE 10 [Steel No. 6-19; copper] V-16 Charpy Yield Tensile transitionNumber Temperature Thickness, Reduction, point, strength, temperature,Reduction practice oi passes range, F. inches percent K s.i. K 5.1. F.Hot rolling 11 2, 200-1, 650 4-- 87. 6 60. 6 91, 7 +20 5 2, 200-1, 4004"-2%" 40. s Continuum rolling 3 1, 400-1, 2}- 1 B3. 0 3 1,- 160-940 1}z 60. 0 107. 8 119. 1 186 ,ixaiqste 01211011862 TABLE 11 [Steel No.7-Bainltlc] V-lfi Ch y Yield Tensile transi t l c -n Number TemperatureThickness, Reduction, point, strength, temperature, Reduction practiceof passes range, F. inches percent K s.i K s.l. F. Hot rolling 2, 200-1,600 4-}- Do 10 2, 200-1 360 4 7 2, 200-1, 140 4"-1 Continuum rolling 21, 140-960 1%" 830 1 920 830" Yield strength (0.2% oflset).

We claim:

1. Method of rolling a steel workpiece containing not more than 0.35percent carbon and not more than a'total of 3 percent of other elementsother than iron comprising:

a. rolling said workpiece in one or more passes as it is cooling from atemperature at which it is austenitic but while its temperature is stillabove the Ar temperature,

b. continuing the rolling of said workpiece in one or more passesincluding at least one reduction pass as it is cooling in thetemperature range between the Ar and the Ar temperatures,

c. continuing the rolling of said workpiece in one or more passesincluding at least one reduction pass as it is cooling in thetemperature range between the Ar, temperature and 600 F., and

d. maintaining conditions such that complete recrystallization does nottake place at any time after the last reduction pass in step (b).

2. Method of rolling a steel workpiece containing not more than 0.35percent carbon and not more than a total of 3 percent of other elementsother than iron comprising:

a. rolling said workpiece in one or more passes as it is cooling from atemperature at which it is austenitic but while its temperature is stillabove the Ar temperature,

b. continuing the rolling of said workpiece in one or more passesincluding at least one reduction pass as it is cooling in thetemperature range between the Ar: and the Ar temperatures,

c. continuing the rolling of said workpiece in one or more passesincluding at least one reduction pass as it is cooling in thetemperature range between the Ar temperature and 600 F., and

d. maintaining conditions such that the percentage recrystallizationdoes not exceed 60 percent at any time after the last reduction pass instep (b).

3. Method of rolling a steel workpiece containing not more than 0.35percent carbon and not more than a total of 3 percent of other elementsother than iron comprising:

a. providing said workpiece at a temperature at which it is essentiallycompletely austenitic,

b. rolling said workpiece in one or more passes including at least onereduction pass as it is cooling in the temperature range between the Arand the Ar temperatures,

c. continuing the rolling of said workpiece in one or more passesincluding at least one reduction pass as it is cooling in thetemperature range between the Ar temperature and 600 F and d.maintaining conditions such that complete recrystallization does nottake place at any time after the last reduction pass in step (b).

4. Method of rolling a steel workpiece containing not more than 0.35percent carbon and not more than a total of 3 percent of other elementsother than iron comprising:

a. providing said workpiece at a temperature at which it is essentiallycompletely austenitic,

b, rolling said workpiece in one or more passes including at least onereduction pass as it is cooling in the temperature range between the Arand the Ar temperatures,

c. continuing the rolling of said workpiece in one or more passesinclu;ing at least one reduction pass as it is cooling in thetemperature range between the Ar, temperature and 600 F., and

d. maintaining conditions such that the percentage recrystallizationdoes not exceed 60 percent at any time after the last reduction pass instep (b).

2. Method of rolling a steel workpiece containing not more than 0.35percent carbon and not more than a total of 3 percent of other elementsother than iron comprising: a. rolling said workpiece in one or morepasses as it is cooling from a temperature at which it is austenitic butwhile its temperature is still above the Ar3 temperature, b. continuingthe rolling of said workpiece in one or more passes including at leastone reduction pass as it is cooling in the temperature range between theAr3 and the Ar1 temperatures, c. continuing the rolling of saidworkpiece in one or more passes including at least one reduction pass asit is cooling in the temperature range between the Ar1 temperature and600* F., and d. maintaining conditions such that the percentagerecrystallization does not exceed 60 percent at any time after the lastreduction pass in step (b).
 3. Method of rolling a steel workpiececontaining not more than 0.35 percent carbon and not more than a totalof 3 percent of other elements other than iron comprising: a. providingsaid workpiece at a temperature at which it is essentially completelyaustenitic, b. rolling said workpiece in one or more passes including atleast one reduction pass as it is cooling in the temperature rangebetween the Ar3 and the Ar1 temperatures, c. continuing the rolling ofsaid workpiece in one or more passes including at least one reductionpass as it is cooling in the temperature range between the Ar1temperature and 600* F., and d. maintaining conditions such thatcomplete recrystallization does not take place at any time after thelast reduction pass in step (b).
 4. Method of rolling a steel workpiececontaining not more than 0.35 percent carbon and not more than a totalof 3 percent of other elements other than iron comprising: a. providingsaid workpiece at a temperature at which it is essentially completelyaustenitic, b, rolling said workpiece in one or more passes including atleast one reduction pass as it is cooling in the temperature rangebetween the Ar3 and the Ar1 temperatures, c. continuing the rolling ofsaid workpiece in one or more passes including at least one reductionpass as it is cooling in the temperature range between the Ar1temperature and 600* F., and d. maintaining conditions such that thepercentage recrystallization does not exceed 60 percent at any timeafter the last reduction pass in step (b).